使用C#未显示实际图像时裁剪图像问题

我正在使用JCrop来裁剪图像.如果我向用户显示实际图像,它工作正常.但是,如果我显示调整大小图像而不是实际图像,那么我将获得调整大小图像的坐标.
然后,我如何基于它裁剪图像？在这里,我正在传递保存图像的图像路径.
简而言之,如果为715 * 350,如果保存图像大小,那么我将在基于CSS的小尺寸弹出窗口中显示它.所以,我将得到那个小尺寸图像的坐标.我正在主图像上应用这些坐标.

我的代码：

using (System.Drawing.Image OriginalImage = System.Drawing.Image.FromFile(Img))
            {
                using (System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(Width,Height))
                {
                    bmp.SetResolution(OriginalImage.HorizontalResolution,OriginalImage.VerticalResolution);

                    using (System.Drawing.Graphics Graphic = System.Drawing.Graphics.FromImage(bmp))
                    {
                        Graphic.SmoothingMode = SmoothingMode.AntiAlias;
                        Graphic.InterpolationMode = InterpolationMode.HighQualityBicubic;
                        Graphic.PixelOffsetMode = PixelOffsetMode.HighQuality;
                        Graphic.DrawImage(OriginalImage,new System.Drawing.Rectangle(0,Width,Height),X,Y,Height,System.Drawing.GraphicsUnit.Pixel);

                        MemoryStream ms = new MemoryStream();
                        bmp.Save(ms,OriginalImage.RawFormat);

                        ms.Close();
                        ms.Flush();
                        ms.Dispose();

                        return ms.GetBuffer();
                    }
                }
            }

public static async Task CropImage()
{
    var client = new WebClient();
    var sourceimg = new Uri(@"http://logonoid.com/images/stack-overflow-logo.png");
    var destination = new FileInfo(Path.Combine(Directory.GetCurrentDirectory(),"logoCropped.png"));
    if (destination.Exists)
        destination.Delete();
    using (Stream sourceStream = await client.OpenReadTaskAsync(sourceimg))
    {
        using (Bitmap source = new Bitmap(sourceStream))
        {
            Rectangle cropzone = new Rectangle(0,256,256);
            using (Bitmap croppedBitmap = source.Clone(cropzone,source.PixelFormat))
            {
                croppedBitmap.Save(destination.FullName,ImageFormat.Png);
            }
        }
    }
}